Reporter cell assays are useful probes of the biological function of a cell, yielding information on the status of the cell. This type of information is not easily obtainable from other classes of assays, such as binding assays or cell surface stains. While reporter cell assays have been performed within reaction well format or flow cytometry format, investigation of the status of at least one cell, is not readily performed. There is need for improvement in this field in order to support basic biological research, pharmaceutical research and development, medical diagnostics and treatment as well as for bioproduction of cells expressing useful biological/chemical species.